I was lucky with this design.
By volume repartition I meant that having enough volume to confortably uphaul (about 90l or more in my case) then you need the volume to be about the same forward and aft of the mast base.
Considering UJ setting for foiling, I prefer to use the distance between the forward bolt ot the tuttle box and the UJ, as distancefromstern depends on tail outline. As you can see, as was the trend when I designed this board, it is rather a no tail. So my set up is 82cm forward of front DTT bolt.
I wish I could sail more often on open sea, but it is much a longer drive for me. Plus the depth and steep bottom slope of this lake makes it ideal for foiling.
If you want to build up your foiling skills, not knowing if you want to go big and wide for slalom like sailing, or small and inboard for freefoiling, I would suggest designing something Tiny like (from Horue). The Horue Tiny is still one of the best and versatile design.
My first dedicated foil board was a Tiny like of about 110l and 190x75cm.
A pic of my two boards :

When I want to go for sailing with my larger and camed sail (challenger Sail Bad 6.3)I use the larger one. But it is very good with a wave sail too. I just feel limited by its width when I want to carve hard, but this only since a few mounths, as I have gained a lot of confidence with my smaller board.
Regarding foil wing ratio, I believe that you should focus more on the profile : each profile is optimised for a specific speed range, and some have a wide range of efficiency, some just aim top speed. There are many trade of made by wing designer.
Depending on what characteristics you're looking for, you'll have to talk a lot with wing designer to get an idea of what they worked on, then figure out how to use it.
Riding in waves would require as long a foil mast you can manage to launch.